Method and apparatus for treating glass on a pressurized fluid bed



Dec. 14, 1965 J. c. FREDLEY ETAL 3,

METHOD AND APPARATUS FOR TREATING GLASS ON A PRESSURIZED FLUID BED Filed Nov. 9, 1962 v 18 Sheets-Sheet 1 FIG. IA

INVENTORS Dec. 14, 1965 J. c. FREDLEY ETAL. 3,223,501 METHOD AND APPARATUS FOR TREATING GLASS ON A PRESSURIZED FLUID BED Filed NOV. 9, 1962 18 Sheets-Sheet 2 INVENTORS JAMES C FREDLEY 6501965 E. SLE/Gl/f'k BY ATTOR/Vf) Dec. 14, 1965 J. c. FREDLEY ETAL 3,223,501

METHOD AND APPARATUS FOR TREATING GLASS ON A PRESSURIZED FLUID BED Filed Nov. 9, 1962 18 Sheets-Sheet 5 RS JAMES c Fkt-DLEY GWL 5:020: 5 SlE/GHTER 4 TT'OENEY Dec. 14, 1965 J. c. FREDLEY ETAL 3,223,501

METHOD AND APPARATUS FOR TREATING GLASS ON A PRESSURIZED FLUID BED Filed Nov. 9, 1962 18 Sheets-Sheet 4 INVENT Jam: c. Fee-0457 GEORGE E. SLE/GHTEK BY A TTOR/VEY Dec. 14, 1965 J. c. FREDLEY ETAL 3,

METHOD AND APPARATUS FOR TREATING GLASS ON A PRESSURIZED FLUID BED Filed Nov. 9. 1962 18 Sheets-Sheet 5 1H L TF3 H J 1: "INVENTORS JAMES c FE'DlEY ""1 BY GEORGE E SZEIG'l/TER I Anne/v57 Dec. 14, 1965 J. c. FREDLEY ETAL 3,223,501

METHOD AND APPARATUS FOR TREATING GLASS ON A PRESSURIZED FLUID BED 18 Sheets-Sheet 6 Filed NOV. 9, 1962 INVENTORS JAMES c. mime-Y z BY GEOkGE e. szsmflrse Dec. 14, 1965 J. c. FREDLEY ETAL METHOD AND APPARATUS FOR TREATING GLASS ON A PRESSURIZED FLUID BED Filed Nov. 9, 1962 18 Sheets-Sheet 7 Dec. 14, 1965 J. c. FREDLEY ETAL 3,223,501

METHOD AND APPARATUS FOR TREATING GLASS ON A PRESSURIZED FLUID BED Filed Nov. 9, 1962 18 Sheets-Sheet 8 FIGJO JNVENTO 5 Jane: 0. new? one: 5. Iii/619754? Dec. 14, 1965 Filed Nov. 9, 1962 METHOD c. FREDLEY ETAL 3,223,501

APPARATUS FOR TREATING GLASS ON A PRESSURIZED FLUID BED l8 Sheets-Sheet 9 FIG."

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METHOD AND APPARATUS FOR TREATING GLASS ON A PRESSURIZED FLUID BED Filed Nov. 9, 1962 18 Sheets-Sheet 13 Fl Ca. \9 J J l l 1 l UNIFORM RADIANT HEATING GLASS MOVEMENT 5 UNIFDRM PRESSURE UNIFORM GAS TEMPERATURE FOR CONVECTiON HEATING OF GLASS SURFACE MODULE PRESSURE PROFILE U U V AVERAGE SUPPORT PRESS!) a J= -ATMosP5|-:R c Pae su a;

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INVENTORS JAMES C FKEDLET 650866 E. SLE/fil/TER Dec. 14, 1965 J. c. FREDLEY ETAL 3,223,501

METHOD AND APPARATUS FOR TREATING GLASS ON A PRESSURIZED FLUID BED Filed Nov. 9, 1962 18 Sheets-Sheet 17 Fl G. 32

INVENTORS JAMES c. FkEDLE) M 05020: 5, sum/175 Dec. 14, 1965 J. c. FREDLEY ETAL 3,223,501

METHOD AND APPARATUS FOR TREATING GLASS ON A PRESSURIZED FLUID BED Filed Nov. 9, 1962 18 Sheets-Sheet 18 INVENTORS JAMES c Feipzsr 95020: a ana /r5 United States Patent vania Filed Nov. 9, 1962, Ser. No. 236676 35 Claims. (Cl. 65-25) This application is a continuation-in-part of our copending application Serial No. 236,103, filed November 7, 1962, now abandoned, which application is, in turn, a continuation-in-part of our copending application Serial No. 209,456, filed July 12, 1962, now abandoned, which application is, in turn, a continuation-in-part of our copending application Serial No. 185,757, filed April 6, 1962, now abandoned, which application is, in turn, a continuation-in-part of our copending application Serial No. 172,335, filed February 9, 1962, which application is, in turn, a continuation-in-part of our copending application Serial No. 139,901, filed September 22, 1961, now abandoned, which application is, in turn, a continuation-inpart of our application Serial No. 31,572, filed May 25, 1960, now abandoned. Reference is also made to our copending applications Serial No. 139,902, filed September 22, 1961, now abandoned; Serial No. 140,135, filed September 22, 1961, now abandoned; Serial No. 140,135, filed September 22, 1961, now abandoned; Serial No. 175,938, filed February 27, 1962, now abandoned; Serial No. 176,050, filed February 27, 1962, now abandoned; Serial No. 178,997, filed March 12, 1962; Serial No. 185,448, filed April 5, 1962; and Serial No. 195,773, filed May 18, 1962, all of which applications are directed to related subject matter. All of the aforesaid applications referred to herein pursuant to 35 U.S.C. 120, are assigned to the assignee of this application.

This invention relates to the fabrication of glass and more particularly to heating of glass and to the transportation and/ or support of hot glass sheets, especially glass at a deformation temperature. It is particularly concerned with such a process when combined with other operations such as bending, tempering, annealing, flattening, or coating such sheets.

Sheets of glass may be fabricated through known manufacturing techniques of bending, tempering, annealing or coating and combinations of such techniques to form end products having characteristics and uses different from the original product. A common feature of these techniques is the heating of glass sheets to a temperature above that at which the major surfaces or the contour thereof will be changed by a deforming stress or contact with solids, hereinafter referred to as deformation temperature. For most plate and Window glass this temperature is around 980 degrees Fahrenheit and above, but usually below a temperature at which the glass becomes molten.

Economic utilization of fabricating equipment requires that the glass sheets undergoing treatment be conveyed while hot.

The necessity of conveying glass at high temperature has heretofore resulted in undesirable deformation or marring of the major surfaces of glass sheets being treated due to physical contact with supporting and conveying apparatus while the glass is at elevated temperatures. The instant invention overcomes this defect common to the known methods of heat treating glass sheets. In addition,

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this invention overcomes further disadvantages peculiar to some of the individual fabricating techniques.

Included in the instant invention are new and useful methods and apparatus for supporting and conveying hot glass. More specifically, methods and apparatus have been devised for supporting and conveying a sheet of glass on a gas bed while the glass is at or above deformation temperature. The gas bed uniformly supports the glass against undesired deformation and eliminates the necessity of contact of the major surfaces of the glass sheet with any solid object while the glass is subject to deformation or impairment. In this manner, the marring or distorting now associated with current fiat glass fabricating processes has been eliminated.

Classical bending of fiat glass consists of heating the sheet while supported over a sand mold and allowing the glass to sag until it conforms to the mold. Such technique is obviously applicable only to custom jobs and does not lend itself to tempering. Small pieces of flat glass are even today bent on solid asbestos-covered convex molds, particularly in cases where the bendsare spherical and the tolerance in surface quality is large. With the advent of curved auto and aircraft lights or windows, there is now demand for large volume production of curved sheet glass of high surface quality. Sometimes the glass is annealed and laminated, sometimes tempered, for safety purposes.

Fabricators of window and plate glass have utilized a variety of techniques heretofore for bending auto and aircraft glass. Simple bends have been produced by suspending fiat parts with tongs, heating the glass above deformation temperature and applying bending moments by application of weighted wires urging the glass to conform to a predetermined simple curve, also by pressing the glass suspended by tongs with complementary malefemale solid molds. Tongs mar the glass where they engage the surface, as do wires or the solid portions of presses.

Horizontal bending :by gravity has been utilized, sheets of glass being mounted singly or in pairs across a ring mold or open affair in which only a small section of the major surface around the periphery of the glass being )bent comes into contact with a mold surface and the glass is allowed to sag to shape under the influence of heat, sometimes aided by moments of force applied through movable mold sections. Because the chord of the curve produced is shorter than the same dimension on the flat pattern, there is relative movement between mold surface and glass while the glass is soft. This pro duces mold marks and scuff. Furthermore, the differential in heat capacity between the mold (usually metal) and the surrounding environment sets up differential stress patterns in the glass whether subsequently annealed or tempered and often produces visible distortion called pie crust. Pie crust is a defect in the glass margins which appears to correspond roughly to the edge of the mold. Usually the glass is conveyed upon the mold during annealing or tempering until fabrication is complete. This requires a large complement of molds to achieve good production rates, another disadvantage.

In utilizing the instant invention for bending, the marring of the surface common to the prior art is overcome. Glass sheets are supported and conveyed over a gas support bed while the sheets are heated to a temperature at which they can bend. Due to the substantial uniformity of support pressure provided by the gas of the instant invention, the contour of the heated sheets may be maintained Within close tolerances. By gradually changing the contour of the supporting gas bed and conveying the heated sheets by edge contact or contact localized at the margins only, the contour of the sheets changes in travel to conform to the supporting force, resulting in sheets formed to a desired curvature. The curved sheets so produced may be either tempered or annealed subsequently, while retaining the established contour on the gas film.

In tempering fiat sheets, the prior art uses one of three alternative means of support. In one, the glass is gripped near an upper margin by tongs and thus is suspended from a carriage riding on a conveyor which may move the glass from a vertical furnace either laterally or vertically to a position between adjacent blowers which quench or temper the glass. Alternatively, the glass may rest at the bot-tom edge on a mesh support carried by the conveyor and be held upright by fingers on each side of the upper edge. In a second alternative, fiat glass is simply conveyed through a furnace and thence between horizontal blowers with the bottom major sunface of the glass supported on rolls of small diameter closely centered so as to diminish the distance between lines of support.

The vertical processes leave tong or finger marks and develop uneven stresses attributable to local heat transfer differentials in the vicinity of the mesh, fingers and tongs.

The roller process leaves roll marks, sculf marks, and other defects, in addition to which a certain degree of wave distortion is inevitably imparted to the sheet as a consequence of the glass undulating over the rolls as it softens in its travel.

In the instant invention, glass sheets, for example, fiat sheets, to be tempered, are supported upon a gas bed exerting a substantially uniform pressure so as to support the sheets against deformation while they are heated to a deformation temperature. Such support can be so effectively achieved that even warped sheets can be flattened. The movement of the sheets along the gas support is controlled through physical means contacting only an edge or marginal portion thereof. After reaching the desired temperature, each sheet is moved between a supporting, relatively cold, flowing gas support and an opposing cold gas flow on the opposite major surface, both having sufficient flow and low temperature to establish the necessary thermal gradient between the surfaces and the interior, and is thus tempered without the marring or distortion characteristic of the prior art.

In addition to eliminating the foregoing disadvantages, the instant invention, through more efiicient and uniform heat transfer, has substantially eliminated the irregular iridescent strain pattern characteristic of tempered glass and has provided a process for fully tempering thinner glass to produce products of higher quality than has been possible under existing production processes.

In known processes of annealing, glass exhibiting undesirably high internal stresses is conveyed on rollers through a lehr where it is reheated substantially to its upper annealing range to allow stresses to relax and is then cooled in a controlled manner through the lower limit of its annealing range. The nonuniform support and the unavoidable slippage between the rollers and the softened glass results in distortion and surface marring of the sheets. In the manner herein disclosed, glass may be reheated and annealed without the attendant disad vantages of the known processes. This is accomplished by supporting and conveying the heated sheets of glass along a gas bed which provides uniform support without physical contact with the major surfaces of the glass.

Coated glass has myriad end uses. Many coatings require heat treatment during fabrication. For instance, in producing flat colored spandrels for architectural purposes, fiat sheet glass is coated cold on one side with a frit or enamel and then fired to glaze the .frit and bond it to the glass surface. Firing temperatures exceed the deformation temperature of the flat glass substrate.

If produce-d on roller le'hrs, wave, bow and other distortion results. If processed while suspended by tongs, tong marks ensue. Usually the product is chilled after firing to produce a semi-temper, or partial strengthening. Full temper within practical quality limitations is well nigh impossible of achievement with existing processes because of lack of control. The heat transfer rate on one side of the sheet differs from that on the other; Existing relatively crude quenching blowers do not permit the control necessary to match the quantum of heat transfer on opposite sides-a practical sine qua non for achieving full temper.

Likewise, there is a desideratum for higher temperature in firing because the durability of the coating is enhanced thereby. The prior art is limited in this -regard because above about 1150 degrees Faherenheit, tongs not only indent but more or less tear the glass along the points of contact, while in the roller system intolerable wave results.

The present invention overcomes all these defects. The coated sheet can be fired at higher temperatures without marring or distortion. It can be tempered to the degree desired by control of the rates of flow in the quenching section.

Again, a variety of useful end products are produced by spraying metallic salt solutions on hot glass. Transparent electroconductive tin oxide coatings are produced when a cold solution of a tin salt such as tin chloride is sprayed on hot glass. Transparent light and heat reflecting films are produced when solutions of cobalt and other metal salts are sprayed cold on hot glass. As in the case of enamels, the inadequacies of the prior art limit the temperature of sheet glass treatment below optimum temperatures desirable in achieving not only maximum durability but other functional attributes suchv as conductivity in conductive films. The glass is marred and distorted in treatment. These deficiencies are overcome in utilizing the present invention.

The broad concept of supporting and conveying sheet material on a gas bed is, of course, known and has been used in many industrial applications. These known methods and apparatus for supporting and conveying sheet material are, however, unsatisfactory for supporting a readily deformable visco-elastic material while the material approaches a deformation temperature. Because the known methods and apparatus are incapable of supporting a deformable visco-elastic sheet of material uniformly over substantially its entire area, their application to the support of glass sheets heated to a temperature at which they readily deform is precluded. Thus, the insulficiencies of design for the purposes herein intended of such a gas film support as disclosed in U.S. Patent No. 1,622,817 to Frederic B. Waldron result in an unacceptable distortion of any glass heated to the temperature at which it will readily deform when supported on a device of the nature disclosed therein.

Applicants have, through the use of the methods and apparatus disclosed herein which form the subject matter of this invention, overcome the above-discussed disadvantages of the known methods of treating, supporting and conveying glass.

In its broader aspects the present invention contemplates the provision of a support system adapted for handling hot glass, or other heat deformable material, in sheet or ribbon form without marring or otherwise producing uncontrolled deformation in the major surfaces, even when the glass or other material is at a deformation temperature.

In accordance with an embodiment of the invention, there is provided a plurality of evenly distributed zones of uniform nominal pressure on the lower side of the sheet adequate to support the sheet element undergoing treatment. Gas flows from a reservoir under higher pressure into such zones, being uniformly throttled between the reservoir and each zone to restrict the passage of gas 

1. A METHOD OF CONVEYING SHEET MATERIAL AT A DEFORMATION TEMPERATURE WHICH COMPRISES ESTABLISHING A PLURALITY OF SEPARATE SPACED GASEOUS PRESSURE SUPPORT ZONES EACH EXERTING AN UPWARD SUPPORTING PRESSURE, EXHAUSTING GAS AT LOWER PRESSURE FROM SAID ZONES AT POINTS ADJACENT SAID ZONES, DISPOSING SHEET MATERIAL ON A PORTION OF SAID ZONES AND IN CONTACT WITH THE GAS THEREOF, THE GAS SUPPORTING THE SHEET MATERIAL, FEEDING GAS INTO SAID ZONES IN AN INITIAL DIRECTION AWAY FROM THE DIRECTION OF THE SUPORT PRESSURE, AND MOVING THE SHEET MATERIAL ACROSS ANOTHER PORTION OF SAID SUPPORT ZONES. 9 APPARATUS FOR PROVIDING FLUID SUPPORT FOR A MOVING SHEET OF GLASS COMPRISING A PLURALITY OF ROWS OF OPEN TOPPED FLUID OUTLETS EACH OF WHICH SUBTENDS A SMALL PORTION OF THE SUPPORT AND EACH HAVING AT LEAST PORTIONS OF 